kernel/linux.git/drivers/xen/manage.c, branch linux-4.16.y

xen/time: do not decrease steal time after live migration on xen

2017-11-02T20:49:41+00:00

After guest live migration on xen, steal time in /proc/stat (cpustat[CPUTIME_STEAL]) might decrease because steal returned by xen_steal_lock() might be less than this_rq()->prev_steal_time which is derived from previous return value of xen_steal_clock(). For instance, steal time of each vcpu is 335 before live migration. cpu 198 0 368 200064 1962 0 0 1340 0 0 cpu0 38 0 81 50063 492 0 0 335 0 0 cpu1 65 0 97 49763 634 0 0 335 0 0 cpu2 38 0 81 50098 462 0 0 335 0 0 cpu3 56 0 107 50138 374 0 0 335 0 0 After live migration, steal time is reduced to 312. cpu 200 0 370 200330 1971 0 0 1248 0 0 cpu0 38 0 82 50123 500 0 0 312 0 0 cpu1 65 0 97 49832 634 0 0 312 0 0 cpu2 39 0 82 50167 462 0 0 312 0 0 cpu3 56 0 107 50207 374 0 0 312 0 0 Since runstate times are cumulative and cleared during xen live migration by xen hypervisor, the idea of this patch is to accumulate runstate times to global percpu variables before live migration suspend. Once guest VM is resumed, xen_get_runstate_snapshot_cpu() would always return the sum of new runstate times and previously accumulated times stored in global percpu variables. Comment above HYPERVISOR_suspend() has been removed as it is inaccurate: the call can return an error code (e.g., possibly -EPERM in the future). Similar and more severe issue would impact prior linux 4.8-4.10 as discussed by Michael Las at https://0xstubs.org/debugging-a-flaky-cpu-steal-time-counter-on-a-paravirtualized-xen-guest, which would overflow steal time and lead to 100% st usage in top command for linux 4.8-4.10. A backport of this patch would fix that issue. [boris: added linux/slab.h to driver/xen/time.c, slightly reformatted commit message] References: https://0xstubs.org/debugging-a-flaky-cpu-steal-time-counter-on-a-paravirtualized-xen-guest Signed-off-by: Dongli Zhang Reviewed-by: Boris Ostrovsky Signed-off-by: Boris Ostrovsky

Merge tag 'for-linus-4.13-rc1-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/xen/tip

2017-07-07T02:11:24+00:00

Pull xen updates from Juergen Gross: "Other than fixes and cleanups it contains: - support > 32 VCPUs at domain restore - support for new sysfs nodes related to Xen - some performance tuning for Linux running as Xen guest" * tag 'for-linus-4.13-rc1-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/xen/tip: x86/xen: allow userspace access during hypercalls x86: xen: remove unnecessary variable in xen_foreach_remap_area() xen: allocate page for shared info page from low memory xen: avoid deadlock in xenbus driver xen: add sysfs node for hypervisor build id xen: sync include/xen/interface/version.h xen: add sysfs node for guest type doc,xen: document hypervisor sysfs nodes for xen xen/vcpu: Handle xen_vcpu_setup() failure at boot xen/vcpu: Handle xen_vcpu_setup() failure in hotplug xen/pv: Fix OOPS on restore for a PV, !SMP domain xen/pvh*: Support > 32 VCPUs at domain restore xen/vcpu: Simplify xen_vcpu related code xen-evtchn: Bind dyn evtchn:qemu-dm interrupt to next online VCPU xen: avoid type warning in xchg_xen_ulong xen: fix HYPERVISOR_dm_op() prototype xen: don't print error message in case of missing Xenstore entry arm/xen: Adjust one function call together with a variable assignment arm/xen: Delete an error message for a failed memory allocation in __set_phys_to_machine_multi() arm/xen: Improve a size determination in __set_phys_to_machine_multi()

xen: don't print error message in case of missing Xenstore entry

2017-06-07T07:48:02+00:00

When registering for the Xenstore watch of the node control/sysrq the handler will be called at once. Don't issue an error message if the Xenstore node isn't there, as it will be created only when an event is being triggered. Signed-off-by: Juergen Gross Reviewed-by: Boris Ostrovsky Signed-off-by: Juergen Gross

init: Introduce SYSTEM_SCHEDULING state

2017-05-23T08:01:38+00:00

might_sleep() debugging and smp_processor_id() debugging should be active right after the scheduler starts working. The init task can invoke smp_processor_id() from preemptible context as it is pinned on the boot cpu until sched_smp_init() removes the pinning and lets it schedule on all non isolated cpus. Add a new state which allows to enable those checks earlier and add it to the xen do_poweroff() function. No functional change. Tested-by: Mark Rutland Signed-off-by: Thomas Gleixner Signed-off-by: Peter Zijlstra (Intel) Reviewed-by: Boris Ostrovsky Acked-by: Mark Rutland Cc: Greg Kroah-Hartman Cc: Juergen Gross Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Steven Rostedt Link: http://lkml.kernel.org/r/20170516184736.196214622@linutronix.de Signed-off-by: Ingo Molnar

xen: modify xenstore watch event interface

2017-02-09T16:26:49+00:00

Today a Xenstore watch event is delivered via a callback function declared as: void (*callback)(struct xenbus_watch *, const char **vec, unsigned int len); As all watch events only ever come with two parameters (path and token) changing the prototype to: void (*callback)(struct xenbus_watch *, const char *path, const char *token); is the natural thing to do. Apply this change and adapt all users. Cc: konrad.wilk@oracle.com Cc: roger.pau@citrix.com Cc: wei.liu2@citrix.com Cc: paul.durrant@citrix.com Cc: netdev@vger.kernel.org Signed-off-by: Juergen Gross Reviewed-by: Paul Durrant Reviewed-by: Wei Liu Reviewed-by: Roger Pau Monné Reviewed-by: Boris Ostrovsky Signed-off-by: Boris Ostrovsky

xen/manage: correct return value check on xenbus_scanf()

2017-02-03T16:26:40+00:00

A negative return value indicates an error; in fact the function at present won't ever return zero. Signed-off-by: Jan Beulich Reviewed-by: Juergen Gross Signed-off-by: Boris Ostrovsky

xenbus: advertise control feature flags

2016-10-24T14:48:40+00:00

The Xen docs specify several flags which a guest can set to advertise which values of the xenstore control/shutdown key it will recognize. This patch adds code to write all the relevant feature-flag keys. Based-on-patch-by: Paul Durrant Signed-off-by: Juergen Gross Reviewed-by: David Vrabel Reviewed-by: Paul Durrant Signed-off-by: David Vrabel

xen: Use correctly the Xen memory terminologies

2015-09-08T17:03:49+00:00

Based on include/xen/mm.h [1], Linux is mistakenly using MFN when GFN is meant, I suspect this is because the first support for Xen was for PV. This resulted in some misimplementation of helpers on ARM and confused developers about the expected behavior. For instance, with pfn_to_mfn, we expect to get an MFN based on the name. Although, if we look at the implementation on x86, it's returning a GFN. For clarity and avoid new confusion, replace any reference to mfn with gfn in any helpers used by PV drivers. The x86 code will still keep some reference of pfn_to_mfn which may be used by all kind of guests No changes as been made in the hypercall field, even though they may be invalid, in order to keep the same as the defintion in xen repo. Note that page_to_mfn has been renamed to xen_page_to_gfn to avoid a name to close to the KVM function gfn_to_page. Take also the opportunity to simplify simple construction such as pfn_to_mfn(page_to_pfn(page)) into xen_page_to_gfn. More complex clean up will come in follow-up patches. [1] http://xenbits.xen.org/gitweb/?p=xen.git;a=commitdiff;h=e758ed14f390342513405dd766e874934573e6cb Signed-off-by: Julien Grall Reviewed-by: Stefano Stabellini Acked-by: Dmitry Torokhov Acked-by: Wei Liu Signed-off-by: David Vrabel

xen: Include xen/page.h rather than asm/xen/page.h

2015-06-17T15:14:18+00:00

Using xen/page.h will be necessary later for using common xen page helpers. As xen/page.h already include asm/xen/page.h, always use the later. Signed-off-by: Julien Grall Reviewed-by: David Vrabel Cc: Stefano Stabellini Cc: Ian Campbell Cc: Wei Liu Cc: Konrad Rzeszutek Wilk Cc: Boris Ostrovsky Cc: netdev@vger.kernel.org Signed-off-by: David Vrabel

xen: Suspend ticks on all CPUs during suspend

2015-04-29T16:10:05+00:00

Commit 77e32c89a711 ("clockevents: Manage device's state separately for the core") decouples clockevent device's modes from states. With this change when a Xen guest tries to resume, it won't be calling its set_mode op which needs to be done on each VCPU in order to make the hypervisor aware that we are in oneshot mode. This happens because clockevents_tick_resume() (which is an intermediate step of resuming ticks on a processor) doesn't call clockevents_set_state() anymore and because during suspend clockevent devices on all VCPUs (except for the one doing the suspend) are left in ONESHOT state. As result, during resume the clockevents state machine will assume that device is already where it should be and doesn't need to be updated. To avoid this problem we should suspend ticks on all VCPUs during suspend. Signed-off-by: Boris Ostrovsky Signed-off-by: David Vrabel